The results from our SBIR Phase II project demonstrated that ?-cyclodextrin derivatives designed to block the transmembrane channel formed by B. anthracis protective antigen can inhibit the cytotoxic effects of anthrax toxin at low- and sub-micromolar concentrations. Several compounds were tested in vivo and showed effective protection in rats challenged with lethal toxin and in mice infected with the spores of B. anthracis Sterne strain. The overall goal of this continuation project is to prove that the most promising candidate compounds are protective in relevant animal models of inhalational anthrax against the deadly Ames strain of Bacillus anthracis. The specific aims of the study are: (1) Synthesis, purification and in vitro characterization of the three previously selected most active 2-cyclodextrin derivatives. (2) Development and validation of analytical methods for the detection of cyclodextrins in biological samples. (3) Efficacy testing of three selected compounds in mice challenged with Bacillus anthracis (Ames Strain) using an aerosol route of infection. (4) Testing of the toxicity and pharmacokinetic properties of the two most potent compounds in rabbits. (5) Efficacy testing of the compounds in rabbits challenged with Bacillus anthracis (Ames Strain) using an aerosol route of infection to select drug candidates with the best protective and pharmacokinetic properties and lowest toxicity. In the long-term, in-depth preclinical tests and a Phase 1 clinical trial in healthy adults to demonstrate the drug's safety and tolerability will lead to the development of a new anti-anthrax treatment. PUBLIC HEALTH RELEVANCE: Bacillus anthracis is widely considered as one of the most likely biological weapons threats;however, there is currently no effective treatment for post-symptomatic inhalational anthrax. Traditional antibiotic therapy does not always work at this stage mainly because of the accumulation of anthrax toxin, which is considered a major virulence factor in anthrax infection. For this reason, there is an urgent need for the development of anti-toxin therapeutics, which could be administered after exposure as a supplement to traditional antibiotic intervention.